It's not difficult to know what supplements to take - the idea of taking a certain vitamin for this and a specific mineral for that is not supported by any food science research at all. It's supported by the for-profit vitamin industry because that's how they make all their money, but after 25 years of that model, we are not healthier as a society. Every human cell requires exactly the same nutrients in exactly the same proportion. That was well-established over 40 years ago but there's a huge profit motivation in not following that model.
I agree with you that getting pushed onto medication can be a trap - you say the doctors know what they are doing, but not necessarily. It depends on how many nutrition courses they have taken in the last 5 years. Probably none. Probably none in medical school either. And every medication has possible side effects.
"Eating right" is no longer sufficient either - our food supply is so nutrient-depleted, it's not surprising that we have so many illnesses and so many chemical imbalances. Even the AMA said in 2002 that a balanced diet is not enough.
You can breast feed or not breast feed, your choice. It's more important, as you say, that you feel healthy and that you take care of yourself so you can be there for your child. So I applaud you for that.
I work in food science and there are tremendous tools available for those who feel weak, for those who have depression and anxiety, for those who are nursing, etc. It's important that we supplement our children as well - look at the high increase in things like ADD and ADHD, Asperger's, food intolerances, etc., and you'll see that we need work in that area as well. We're seeing kids get great and measurable results in just a few weeks, and sometimes adults too (or at least within 2 months). So there is plenty that can be done. Looking at the science of epigenetics, patents, clinical studies even on food products, absence of warning labels, etc. are all useful ways of evaluating supplements. Just going by "all natural" is not a good guideline. Something made in a lab with natural ingredients mixed together must, by law, be called "artificial" but it may well be purer and of higher quality than what you find "in nature". So don't be misled by claims in this area. It's hard to find a lot that meet those criteria but it's not impossible. You just have to stop listening to commercials that tell you nothing.